Whenever jumping straight down, you can be fatally injured if you land stiff-legged. One way to avoid the injury is to bend your knees on landing to decrease the force of the impact. A 75 kg man just before contact with the ground has a speed of 6.4 m/s.
Q1. In a stiff-legged landing he comes to halt in 2.0 ms. Find out the average net force which acts on him throughout this time.
Q2. Whenever he bends his knees, he comes to a halt in 0.10s. Find out the average net force now.
Q3. Throughout the landing, the force of the ground on the man points upward, whereas the force due to gravity points downward. The average net force acting on the man comprises both of such forces. Taking into account the directions of the forces, determine the force of the ground on the man in parts (1) and (2).